Commercial waters, such as those used in paper systems, cooling systems, mining systems, and metal systems, are susceptible to contamination and fouling. In order to control such fouling, such waters have been chemically treated generally by trial-and-error methodology. Either too much or too little chemical is used, which is unsatisfactory. Such fouling may be of the biological type or of the non-viable/chemical type. With respect to biological fouling, when it reaches a certain level, it becomes necessary to shut down the system for maintenance.
For example, in a paper system, when microbiological fouling in a white water reaches a certain biological level, it results in making rejectable paper that is costly to paper production. More specifically, the sessile portion of microbial activity causes deposits which are difficult to monitor. When sloughing of the deposits occurs in a paper machine, runability of the machine is affected by increased sheet defects and even paper breaks. At that time the system must be shut down for maintenance, resulting in downtime which interrupts production. It must be cleaned or "boiled out" before the system can be placed back in operation to make acceptable paper. With regard to controlling biological fouling, biocides are added to the water to kill the bacteria or microbes.
Current systems for measuring fouling lack sensitivity, require excessive maintenance, and are not automated. The only method now for differentiating between bacteriological fouling and chemical fouling is through use of destructive testing which measures "sliminess" subjectively, plate counts on a defined portion of the population, or microbial activity.
Dissolved oxygen (DO) probes have been suggested for detecting microbial activity since it is known that high levels of bacteria in fluids decrease dissolved oxygen levels. However, they are limited due to chemical fouling which gradually reduces the efficacy to measure accurate DO levels.
Further, DO probes have been used to measure microbial activity in solutions. Where the dissolved oxygen drops, it is assumed that microbial growth is occurring and the system is contaminated. However, dissolved oxygen can drop due to changes in air supply, probe-surface fouling, temperature variation, or a number of factors, thereby rendering the use of the DO probes unreliable. Thus, reliable measurement of microbiological fouling in processed waters has not been possible.